Liu Hong, Bolton Judy L, Thatcher Gregory R J
Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, 60612-7231, USA.
Chem Res Toxicol. 2006 Jun;19(6):779-87. doi: 10.1021/tx050326r.
The benzothiophene selective estrogen receptor modulators (SERMs), raloxifene and arzoxifene, in the clinic or clinical trials for treatment of breast cancer and postmenopausal symptoms, are highly susceptible to oxidative metabolism and formation of electrophilic metabolites. 4'F-DMA, fluoro-substituted desmethyl arzoxifene (DMA), showed attenuated oxidation to quinoids in incubation with rat hepatocytes as well as in rat and human liver microsomes. Incubations of 4'F-DMA with hepatocytes yielded only one glucuronide conjugate and no GSH conjugates, whereas DMA underwent greater metabolism giving two glucuronide conjugates, one sulfate conjugate, and two GSH conjugates. Phase I and phase II metabolism were further evaluated in human small intestine microsomes and in human intestinal Caco-2 cells. In comparison to DMA, 4'F-DMA formed significantly less glucuronide and sulfate conjugates. The formation of quinoids was further explored in hepatocytes in which DMA was observed to give concentration- and time-dependent depletion of GSH accompanied by damage to DNA, which showed inverse dependence on GSH; in contrast, GSH depletion and DNA damage were almost completely abrogated in incubations with 4'F-DMA. 4'F-DMA shows ligand binding affinity to estrogen receptor (ER)alpha and ERbeta with similarity to both raloxifene and to DMA. ER-mediated biological activity was measured with the ERE-luciferase reporter system in transfected MCF-7 cells and Ishikawa cells, and in MCF-7 cells, proliferation was measured. In all systems, 4'F-DMA exhibited anitestrogenic activity of comparable potency to raloxifene but did not manifest estrogenic properties, mirroring previous results on inhibition of estradiol-mediated induction of alkaline phosphatase activity in Ishikawa cells. These results suggest that 4'F-DMA might be an improved benzothiophene SERM with similar antiestrogenic activity to raloxifene but improved metabolic stability and attenuated toxicity, showing that simple chemical modification can abrogate oxidative bioactivation to potentially toxic metabolites without loss of activity.
苯并噻吩选择性雌激素受体调节剂（SERM）雷洛昔芬和阿佐昔芬，在治疗乳腺癌和绝经后症状的临床应用或临床试验中，极易发生氧化代谢并形成亲电代谢产物。4'F-DMA，即氟代去甲基阿佐昔芬（DMA），在与大鼠肝细胞以及大鼠和人肝微粒体共同孵育时，其氧化生成醌类的过程有所减弱。4'F-DMA与肝细胞共同孵育仅产生一种葡萄糖醛酸结合物，未产生谷胱甘肽（GSH）结合物，而DMA的代谢程度更高，产生了两种葡萄糖醛酸结合物、一种硫酸结合物和两种GSH结合物。在人小肠微粒体和人肠Caco-2细胞中进一步评估了I相和II相代谢。与DMA相比，4'F-DMA形成的葡萄糖醛酸和硫酸结合物明显更少。在肝细胞中进一步探究了醌类的形成，观察到DMA会导致GSH浓度和时间依赖性消耗，并伴有DNA损伤，且这种损伤与GSH呈负相关；相反，在与4'F-DMA共同孵育时，GSH消耗和DNA损伤几乎完全消除。4'F-DMA对雌激素受体（ER）α和ERβ显示出配体结合亲和力，与雷洛昔芬和DMA相似。在转染的MCF-7细胞和石川细胞中，用雌激素反应元件 - 荧光素酶报告系统测量ER介导的生物活性，并在MCF-7细胞中测量增殖。在所有系统中，4'F-DMA表现出与雷洛昔芬相当的抗雌激素活性，但未表现出雌激素特性，这与之前关于抑制石川细胞中雌二醇介导的碱性磷酸酶活性诱导的结果一致。这些结果表明，4'F-DMA可能是一种改良的苯并噻吩SERM，具有与雷洛昔芬相似的抗雌激素活性，但代谢稳定性更高且毒性减弱，表明简单的化学修饰可以消除氧化生物活化形成潜在有毒代谢产物的过程，而不会丧失活性。
